Competing magnetic phases in LnSbTe (Ln = Ho and Tb)

TL;DR

This study uncovers complex magnetic phase coexistence and competition in LnSbTe topological semimetals, revealing multiple magnetic orders below the Néel temperature through neutron diffraction and symmetry analysis.

Contribution

It provides the first detailed neutron diffraction analysis of magnetic phases in LnSbTe (Ln=Ho, Tb), identifying multiple propagation vectors and complex magnetic structures.

Findings

Multiple magnetic phases coexist below TN.

Magnetic structures described by four propagation vectors.

Temperature-dependent transition from commensurate to incommensurate phases.

Abstract

The interplay between topological electronic structure and magnetism may result in intricate physics. In this work, we describe a case of rather peculiar coexistence or competition of several magnetic phases below a seemingly single antiferromagnetic transition in LnSbTe (Ln = Ho and Tb) topological semimetals, the magnetic members of the ZrSiS/PbFCl structure type (space group P4/nmm). Neutron diffraction experiments reveal a complex multi-step order below TN = 3.8 K (Ln = Ho) and TN = 6.4 K (Ln = Tb). Magnetic phases can be described using four propagation vectors: k1 = (1/2 0 0) and k2 = (1/2 0 1/4) at the base temperature of 1.7 K, which transform into incommensurate vectors k1' = (1/2 - d 0 0), k3 = (1/2 - d 0 1/2) at elevated temperatures in both compounds. Together with the refined models of magnetic structures, we present the group-theoretical analysis of the magnetic symmetry of the proposed solutions. These results prompt further investigations of the relation between the electronic structure of those semimetals and the determined antiferromagnetic ordering existing therein.